Gears are commonly lubricated with lubricating grease before delivery and are thus delivered to the customer in a condition ready for use. Because the gears are often not transported in their installed position but, e.g., lying flat, and the lubricating grease releases oil after even a relatively short storage period, this oil may run out of gearbox openings.
This problem occurs, for example, in landing gears that are to be mounted in pairs on semi-trailers of tractor-trailer units. They essentially comprise a support tube with an inner tube that can be telescoped by means of a drive shaft and a gear mechanism.
The major drawback of the leaking oil, in addition to the environmental pollution it causes, is that the oil runs down on the outside of the gearbox and must be removed in a time-consuming process prior to any subsequent paint job. Otherwise it is impossible to obtain a satisfactory painting result.
It has therefore been attempted in the manufacture of the jacks to make the gearbox completely oil-tight to the outside. In practice, however, the results were only partially satisfactory. Although it was possible to obtain a seal in the area of a lid sealing the support tube by introducing a sealing compound between the lid and the support tube and to seal the feed-through of the primary shaft, a solution to the problem of sealing the connecting shaft opening has thus far remained elusive.